The invention relates generally to an active matrix panel and more particularly to a high density active matrix panel formed with thin film transistors, for driving a liquid crystal display (LCD).
A conventional active matrix liquid crystal display panel including a matrix of liquid crystal picture elements formed with thin film transistors (TFT""s) on a transparent substrate is described in Morozumi et al., xe2x80x9cBlack and White and Color Liquid Crystal Video Displays Addressed by Polysilicon TFTsxe2x80x9d, SID-83 Digest, pp. 156-57 and is shown in FIG. 19. A monocrystalline silicon MOS integrated gate line driver circuit 4xe2x80x2 for driving a plurality of gate lines 4axe2x80x2 and a source line driver circuit 4 for driving a plurality of orthoganol source lines 4a are formed on a flexible substrate 3. An active matrix panel 1 includes a matrix of liquid crystal picture elements at the cross-over of respective gate lines 4axe2x80x2 and source lines 4a and a plurality of electrical connection pads 5. Driving circuits 4 and 4xe2x80x2 are electrically coupled to panel 1 at pads 5. Both flexible substrate 3 and panel 1 are mounted on a substrate 6 and integrated driver circuits 4 and 4xe2x80x2 are electrically coupled to other circuitry (not shown).
Such conventional active matrix panels can provide viewable displays, but they can have the following disadvantages.
1. Inadequate Resolution
Flexible substrate 3 and source lines 4a and gates lines 4axe2x80x2 of active matrix panel 1 are electrically coupled at pads 5. Accordingly, the picture elements cannot be sufficiently densely spaced because of the space occupied by pads 5. This interferes with mass production of active matrix panels having a picture element pitch of 100 xcexcm or less and prevents high resolution.
2. Inadequate Display Device Miniturization
Driver integrated circuits 4 and 4xe2x80x2 are located outside of panel 1 on substrate 6. Accordingly, active matrix panel 1 occupies only about xc2xc or ⅕ of the surface area of substrate 6. Consequently, display devices including conventionally formed active matrix panels are undesirably larger than the picture element matrix portion of the entire panel. This makes it inconvenient to include conventional active matrix panels when miniaturization is needed, such as for a micro-monitor which can be used as an electric view finder for a video camera.
3. High Manufacturing Costs
Manufacturing a conventional display including an active matrix panel requires many connections as follows. Active matrix panel 1 is connected to flexible substrate 3; driver integrated circuit 4 is connected to flexible substrate 3; and flexible substrate 3 is mounted on mounting substrate 6. These multiple connection steps increase manufacturing costs.
4. Low Reliability
Because conventional active matrix panels require so many connections, when stress is applied to the panel, these connections can come apart. This affects the reliability of the entire display and increases costs because extra measures must be undertaken to compensate for the possibility of disconnections.
Accordingly, it is desireable to develop an improved active matrix panel which does not have the shortcomings of conventional active matrix panels.
Generally speaking, in accordance with the invention, an active matrix device includes a substrate with a matrix of thin film transistor switching elements formed thereon. A gate line driver circuit and/or a source line driver circuit includes thin film transistors in a complementary metal oxide semiconductor (CMOS) configuration formed on the substrate having the same cross-sectional structure as the switching elements. The driver circuit thin film transistors are either of the P type of N type. The thin film transistors in a CMOS configuration are also referred to herein as complementary thin film transistors.
In one embodiment, the gate line driver circuit and/or the source line driver circuit on the panel substrate includes a static shift register formed of complementary thin film transistors. In another embodiment, the gate line driver circuit and/or the source line driver circuit include P-type and N-type thin film transistor in which the P-type thin film transistor includes acceptor impurities in the source region and drain region and the N-type thin film transistor includes donor impurities having a higher concentration than the acceptor impurities in the source and drain regions. Alternatively, the P-type thin film transistor includes donor impurities and acceptor impurities with a higher concentration of acceptor impurities than the donor impurities in the source region and drain region. The gate length of the P-type and N-type thin film transistors forming the gate line and source line driver circuits is shorter than the gate length of the thin film transistors of the active element matrix.
Accordingly, it is an object of the invention to provide an improved active matrix panel.
Another object of the invention is to provide an active matrix panel that is low in price and high in resolution and reliability.
A further object of the invention is to provide an active matrix panel which has low active element pitch.
Still another object of the invention is to provide an improved active matrix liquid crystal display panel having a high density of picture elements.
Still a further object of the invention is to provide an improved miniaturized active matrix panel.
Yet another object of the invention is to provide an improved active matrix panel that can be used as an electric view finder for a video camera, a monitor for a portable VCR and the like.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and drawings.
The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the article possessing the features, properties and the relation of elements, which are exemplified in the following detail disclosure, and the scope of the invention will be indicated in the claims.